1. Field of the Invention
This invention relates to a positive sensitive resin composition comprising a novel copolymer of 4-(1-methylethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid (PIPE copolymer), an ether-bond-containing olefinic unsaturated compound and an acid-generating agent, as well as a process for forming a resist pattern therewith. In particular, it relates to a positive sensitive resin composition comprising a copolymer of 4-(1-methylethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid useful as a base polymer, an ether-bond-containing olefinic unsaturated compound and an acid-generating agent, as well as a process for forming a resist pattern by applying or adhering the composition to a substrate and then irradiating it with an active energy beam such as ultraviolet rays, visible light and heat rays for developing it.
2. Description of the Related Art
A resist material in combination with an exposure technique has been utilized in lithography such as patterned circuit formation in an electron device and printing.
An application of such patterned circuit formation in an electron device may be, for example, a process for manufacturing a color filter for a variety of multicolored liquid-crystal color displays such as a liquid-crystal color television.
Such a color filter has been conventionally manufactured by, for example, screen printing and electrodeposition. However, as a color display has been improved for its resolution, it has been more important to refine a pattern. Thus, a variety of patterning processes utilizing photolithography has been investigated.
For example, JP-A 8-94827 has disclosed a process for manufacturing a color filter comprising the steps of [1] forming a transparent conductive layer on a transparent substrate; [2] forming a positive photosensitive coating layer; [3] exposing a part of the transparent conductive layer; [4] forming a colored area by electrodeposition; and [5] repeating the steps [3] and [4] as required. Of these steps, a pattern refinement level depends on the steps [2] and [3], in which photolithography is used. In particular, it significantly depends on a positive photosensitive composition applied on the transparent conductive layer. The above invention employs a positive photosensitive composition essentially comprising (a) a polymer containing both carboxyl and hydroxyphenyl groups in one molecule, (b) a compound containing two or more vinyl ether groups in one molecule, and (c) a compound generating an acid by irradiating an active energy beam.
This photosensitive composition is developed as follows; by heating the film on which the positive photosensitive composition has been applied, an addition reaction of the carboxyl group and/or hydroxyphenyl group with the vinyl ether group forms a crosslink, which is insoluble to a solvent or an alkali developing solution, and then, after irradiating with an active energy beam and then, as necessary, heating the film, an acid generated in the irradiated area acts as a catalyst to cleave the crosslink structure and thus to again make the irradiated area soluble to a solvent or an alkali developing solution. For further improving a resolution, a preferable polymer (base polymer) in a positive photosensitive composition is one containing both carboxyl and hydroxyphenyl groups in one molecule which meets all the following five requirements as much as possible;
(a) a higher solubility to a solution which solves a crosslinking agent, an acid-generating gent and others (solvent solubility);
(b) a certain dissolution rate of the cloven crosslink moieties in an alkali developing solution after exposure (dissolution rate in an alkali developing solution);
(c) good diffusivity of an acid generated by irradiation with an active energy beam (acid diffusivity);
(d) transparency of a photosensitive coating at an exposure wavelength (transparency); and
(e) thermal stability during the heating step after application of the film and exposure (thermal stability).
As an example of a polymer meeting these requirements somewhat, a copolymer from p-hydroxystyrene, n-butyl acrylate and acrylic acid has been disclosed in, for example, JP-As 8-94827 and 8-94829. We have, however, investigated the copolymer for its performance and have concluded that it is insufficiently soluble in a solvent or thermally stable.
JP-A 61-293249 has disclosed a binary copolymer of 4-(1-methylethenyl)phenol and n-butyl acrylate as an example of a copolymer for a resin composition exhibiting damping property. The copolymer has an extremely lower dissolution rate in an alkali developing solution and is poorly compatible with a vinyl ether compound. It cannot be, therefore, used as it is.
An objective of this invention is to provide a positive sensitive resin composition useful as the above photoresist material as well as a process for forming a resist pattern using the composition.
We have prepared a variety of copolymers as a resin component in a positive sensitive resin composition, using 4-(1-methylethenyl)phenol and different monomers, to investigate them for their relationship between their basic physical properties and structures, and then have surprisingly found that a copolymer of 4-(1-methyl-ethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid as structural units in a particular composition ratio can meet all the above five requirements for a photoresist material ((a) solvent solubility, (b) dissolution rate in an alkali developing solution, (c) acid diffusivity, (d) transparency and (e) thermal stability).
This invention provides
(I) A positive sensitive resin composition comprising a base polymer, an ether-bond-containing olefinic unsaturated compound and an acid-generating agent, where the base polymer is a copolymer comprising the structural units represented by formula (1): 
where R1 is hydrogen or methyl and R2 is C1-C6 straight or branched unsubstituted alkyl or C1-C6 straight or branched substituted alkyl, and formula (3): 
where R3 is hydrogen or methyl,
wherein a, b and c are 0.05 to 0.7, 0.15 to 0.8 and 0.01 to 0.5, respectively and a+b+c=1;
(II) A positive sensitive resin composition described in (I) where a compounding ratio of the copolymer comprising the structural units represented by formulas (1) to (3) and the ether-bond-containing olefinic unsaturated compound is 0.5 to 50/99.5 to 50 wt % as a ratio of copolymer/unsaturated compound based on their total wt % values, and the amount of the acid-generating agent is 0.1 to 40 wt parts to 100 wt parts of the total amount of the copolymer and the olefinic unsaturated compound;
(III) A positive sensitive resin composition described in (I) where R2 in the structural unit represented by formula (2) is C1-C6 straight or branched unsubstituted alkyl or C1-C6 straight or branched hydroxylated alkyl;
(IV) A positive sensitive resin composition described in (I) where R2 in the structural unit represented by formula (2) is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and 2-hydroxyethyl;
(V) A positive sensitive resin composition described in (I) where a material giving the structural unit represented by formula (2) is a (meth)acrylate selected from the group consisting of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate and 2-hydroxyethyl methacrylate;
(VI) A positive sensitive resin composition described in (I) where for the copolymer, a in formula (1) is 0.20 to 0.45, b in formula (2) is 0.25 to 0.70, and c in formula (3) is 0.15 to 0.40, and a+b+c=1;
(VII) A positive sensitive resin composition described in (I) or (V) where the copolymer comprising the structural units represented formulas (1), (2) and (3) is an alternating copolymer comprising the structural units represented by formula (4): 
where R1 is hydrogen or methyl and R2 is C1-C6 straight or branched unsubstituted alkyl or C1-C6 straight or branched substituted alkyl, and formula (5): 
where R3 is hydrogen or methyl, in which the total content of these structural units is at least 60 mol %;
(VIII) A positive sensitive resin composition described in any of (I) to (VII) comprising a photosensitizer;
(IX) A positive sensitive resin composition described in (VIII) where a compounding ratio of the copolymer comprising the structural units represented by formulas (1) to (3) and the ether-bond-containing olefinic unsaturated compound is 0.5 to 50/99.5 to 50 wt % as a ratio of copolymer/unsaturated compound based on their total wt % values; the amount of the acid-generating agent is 0.1 to 40 wt parts to 100 wt parts of the total amount of the copolymer and the olefinic unsaturated compound; and the amount of the photosensitizer is 0.1 to 20 wt parts to 100 wt parts of the total amount of the copolymer, the olefinic unsaturated compound and the acid-generating agent;
(X) A positive ultraviolet sensitive resist comprising a composition described in any of (I) to (VII), whose part irradiated with ultraviolet rays is soluble or dispersible in an organic solvent or an aqueous developing solution, and whose unirradiated part is substantially insoluble and undispersible in an organic solvent or an aqueous developing solution;
(XI) A positive thermally sensitive resist comprising a composition described in any of (I) to (VII), whose part irradiated with heat rays is soluble or dispersible in an organic solvent or an aqueous developing solution, and whose unirradiated part is substantially insoluble and undispersible in an organic solvent or an aqueous developing solution;
(XII) A positive visible-light sensitive resist comprising a composition described in (VIII) to (IX), whose part irradiated with visible light is soluble or dispersible in an organic solvent or an aqueous developing solution, and whose unirradiated part is substantially insoluble and undispersible in an organic solvent or an aqueous developing solution;
(XIII) An organic-solvent type resin composition which is prepared by dissolving or dispersing the positive sensitive resin composition described in (I) to (IX) in an organic solvent.
(XIV) An aqueous resin composition which is prepared by dissolving or dispersing the positive sensitive resin composition described in (I) to (IX) in water.
(XV) An aqueous resin composition described in (XIV) wherein the dissolving or dispersing is carried out by neutralizing an anionic group in the positive sensitive resin composition with an alkali.
(XVI) A positive dry film comprises a substrate and a resist film, where the resist film is formed by applying a positive sensitive resin composition described in (I) to (IX) to a surface of the substrate.
(XVII) A process for forming a resist pattern consisting essentially of the steps of:
(1) applying a positive sensitive resin composition described in any of (I) to (IX) to a substrate surface to form a resist film;
(2) irradiating the resist film on the substrate with an active energy beam directly or via a mask film to form a desired pattern (image) on the film; and
(3) developing the resist film to form a resist pattern on the substrate;
(XVIII) A process for forming a resist pattern consisting essentially of the steps of:
(1) applying a positive sensitive resin composition described in any of (I) to (IX) to a supporting substrate surface to form a positive dry film comprising a solid positive sensitive resin film;
(2) adhering the dry film on an adhered substrate surface in a manner that the adhered substrate surface faces the resin film of the dry film;
(3) irradiating the dry film surface with an active energy beam directly or via a mask film with or without peeling off the supporting substrate of the dry film, to form a desired pattern; and
(4) developing the resist film, after peeling off the supporting substrate when it has not been removed in the step (3), to form a resist pattern on the substrate.
This invention involves a positive sensitive resin composition comprising a copolymer of 4-(1-methyl-ethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid, an ether-bond-containing olefinic unsaturated compound, and an acid-generating agent. A resist film formed from the composition may be, therefore, heated to be a crosslinked film considerably resistant to a developing solution, whose part irradiated with an active energy beam may be in turn cleaved crosslink to become soluble in a developing solution. The resist film may be, therefore, highly effective for forming a fine and sharp resist pattern.